5.4-stable review patch. If anyone has any objections, please let me know.
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From: Tomas Glozar tglozar@redhat.com
[ Upstream commit 36c75ce3bd299878fd9b238e9803d3817ddafbf3 ]
nd_region_acquire_lane uses get_cpu, which disables preemption. This is an issue on PREEMPT_RT kernels, since btt_write_pg and also nd_region_acquire_lane itself take a spin lock, resulting in BUG: sleeping function called from invalid context.
Fix the issue by replacing get_cpu with smp_process_id and migrate_disable when needed. This makes BTT operations preemptible, thus permitting the use of spin_lock.
BUG example occurring when running ndctl tests on PREEMPT_RT kernel:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 4903, name: libndctl preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 Preemption disabled at: [<ffffffffc1313db5>] nd_region_acquire_lane+0x15/0x90 [libnvdimm] Call Trace: <TASK> dump_stack_lvl+0x8e/0xb0 __might_resched+0x19b/0x250 rt_spin_lock+0x4c/0x100 ? btt_write_pg+0x2d7/0x500 [nd_btt] btt_write_pg+0x2d7/0x500 [nd_btt] ? local_clock_noinstr+0x9/0xc0 btt_submit_bio+0x16d/0x270 [nd_btt] __submit_bio+0x48/0x80 __submit_bio_noacct+0x7e/0x1e0 submit_bio_wait+0x58/0xb0 __blkdev_direct_IO_simple+0x107/0x240 ? inode_set_ctime_current+0x51/0x110 ? __pfx_submit_bio_wait_endio+0x10/0x10 blkdev_write_iter+0x1d8/0x290 vfs_write+0x237/0x330 ... </TASK>
Fixes: 5212e11fde4d ("nd_btt: atomic sector updates") Signed-off-by: Tomas Glozar tglozar@redhat.com Reviewed-by: Ira Weiny ira.weiny@intel.com Reviewed-by: Vishal Verma vishal.l.verma@intel.com Signed-off-by: Ira Weiny ira.weiny@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/nvdimm/region_devs.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/drivers/nvdimm/region_devs.c +++ b/drivers/nvdimm/region_devs.c @@ -898,7 +898,8 @@ unsigned int nd_region_acquire_lane(stru { unsigned int cpu, lane;
- cpu = get_cpu(); + migrate_disable(); + cpu = smp_processor_id(); if (nd_region->num_lanes < nr_cpu_ids) { struct nd_percpu_lane *ndl_lock, *ndl_count;
@@ -917,16 +918,15 @@ EXPORT_SYMBOL(nd_region_acquire_lane); void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane) { if (nd_region->num_lanes < nr_cpu_ids) { - unsigned int cpu = get_cpu(); + unsigned int cpu = smp_processor_id(); struct nd_percpu_lane *ndl_lock, *ndl_count;
ndl_count = per_cpu_ptr(nd_region->lane, cpu); ndl_lock = per_cpu_ptr(nd_region->lane, lane); if (--ndl_count->count == 0) spin_unlock(&ndl_lock->lock); - put_cpu(); } - put_cpu(); + migrate_enable(); } EXPORT_SYMBOL(nd_region_release_lane);